1. Field of the invention
This invention relates to an electrode and more particularly to an electrode for secondary batteries in which alkali metals such as lithium, potassium, or the like are used as a dopant. It also relates to a method for the production of such an electrode.
2. Description of the prior art
As an electrode for conventional secondary batteries in which alkali metals such as lithium, potassium, or the like are used as a dopant, the graphite electrode is well known in which a graphite material having an interlayer spacing of from 0.337 to 0.356 nm is used as an active material for the said electrode (U.S. Ser. No. 030,886 now U.S. Pat. No. 4,863,814).
The graphite material has a structure which is constituted of hexagonal net faces made of carbon atoms, which are spread and stacked over the entire region. In particular, when these hexagonal net faces are stacked in a quite regular manner, their interlayer spacing is equal to 0.3354 nm. When the hexagonal net faces are stacked in a less regular manner, their interlayer spacing increases gradually with increasing irregularity. The graphite material used for conventional electrodes has a distribution of interlayer spacings in the narrow region within the above-mentioned range.
However, such conventional electrodes are disadvantageous in that their electrochemically charging-discharging capacity is small, because the graphite material used as an active material has an interlayer spacing in the narrow region. In particular, the charging-discharging capacity at lower electric potentials, which becomes important when the electrode is combined with an appropriate positive electrode to form a battery, is small. Actually, the charging-discharging capacity at lower electric potentials in the range of 0 to +0.5 V based on that of a lithium reference electrode amounts to less than 180 mA.h per milligram of graphite material.